From Dek Tech:
Bloons Tower Defense 4 a.k.a Balloon Tower Defense 4 is an excellent flash game where a Bloons Super Monkey shoots balloons in defense of his tower. Bloons Tower Defense 4 is long awaited sequel to the Bloons Tower Defense family (Bloons Tower Defense 1, Bloons Tower Defense 2, and Bloons Tower Defense 3). In Bloons TD4 you have a lot of options to use to protect your base including Super Monkey with Plasma Lasers, Cannons with MOABs, Air Assalut, Remote Morters, and more. There are over 9 tracks to play on with varying degrees of difficulty from Easy, to Medium and Hard. If you are new to Bloons Tower Defense games, you can easily start on Bloons Tower Defense 4 without ever having played Bloons Tower Defense 3 (or any of the previous versions for that matter). Start with a new game and just select the first track on easy mode. You start the game with money and earn more for each balloon which you destroy. As you beat levels Bloons Tower Defense 4 unlocks bigger and better weapons to help defend the tower, however as your level increases so does the amount and variety of balloons (lead balloons, fast balloons, steel balloons, and much much more). The balloons run along a course, and if they are able to reach the end you lose a heart. If you loose all of your hearts you loose the game. Bloons Tower Defense 4 is extremely addicting, and the best single game in the Bloons Tower Defense family. This version of Bloons Tower Defense 4 is a stand alone version which you can play offline at any time. Play Bloons Tower Defense 4 now and save your Bloon Super Monkey's Tower forever.